US 2011/0165816 A1 discloses a laser beam irradiation apparatus which irradiates a laser beam onto a sealing element disposed between a first substrate and a second substrate so as to seal the first substrate and the second substrate. The laser beam has a beam intensity which increases from a center portion to an end portion of the laser beam on a surface which is perpendicular to a proceeding direction of the laser beam. The beam intensity at the center portion of the laser beam is not larger than half of the beam intensity at the end portion of the laser beam, wherein the beam profile is symmetric relative to the proceeding direction of the laser beam.
If the sealing element is curved, the laser beam has to be moved along this curved line, wherein in this case in the curve an inner part of the sealing element will receive a larger laser beam intensity than an outer part of the sealing element. This can lead to an inhomogeneous sealing, which can result in sealing errors.